ES2466265T3 - Procedure for the extraction of nickel, cobalt and other base metals from laterite ores by leaching in a pile and products containing nickel, cobalt and other metals from laterite ores - Google Patents

Abstract

Process for the extraction of nickel, cobalt and other metals from laterite ores by means of heap leaching, characterized in that it comprises a crushing (I) that obtains a maximum grain size of between approximately 25.0 mm and approximately 50.0 mm mm in a secondary crushing, and a maximum grain size between about 12.5 mm and about 6.30 mm in tertiary crushing, agglomeration (II), stacking (III) and heap leachate (IV) stages, the latter being stage a continuous countercurrent heap leachate system with two or more stages, which has two phases, one of which is composed of the ore (solute) and the other composed of the leachate solution, or solvent, which are supplied in opposite ends of the series of stages and flow in opposite directions until, at the end of the leachate in the last stage, its solute is removed and a new stage is introduced at the first position comprising new ore (solute) to be leached through the solvent solution that is introduced from the last stage, percolating or flowing through all the previous stages until it reaches the first stage, which is separated if it is loaded with target metals (PLS).

Description

Procedure for the extraction of nickel, cobalt and other base metals from laterite ores by leaching in a pile and products containing nickel, cobalt and other metals from laterite ores

The present invention comprises a process for the extraction of nickel, cobalt, zinc, iron, and copper, between

5 other metals, from laterite ores, with less investment and operating costs than the procedures known to the person skilled in the art. The process according to the invention uses heap leaching, which is a process of extracting soluble components from a mixture of solid laterite stacked by percolation with acid solutions.

State of the art

10 In general, extractive metallurgy is defined as the science and art of extracting metals from minerals and / or the materials that contain them by physical and chemical procedures. Extractive metallurgy can be divided into three main branches: hydrometallurgy, pyrometallurgy, and electrometallurgy.

Hydrometallurgy is the technique of metal extraction by physicochemical procedures by wet route; Pyrometallurgy involves the use of physicochemical procedures by dry route at elevated temperatures; and the

Electrometallurgy refers to the use of electrolytic procedures. Normally, electrometallurgy is integrated into the other two procedures, where electrolysis in aqueous medium is used in hydrometallurgy, and electrolysis in molten media is used in pyrometallurgy.

The extractive metallurgy is also based on various unit operations to facilitate and enhance the concentration and / or separation of metals, which include, among others: dilaceration procedures (crushing and grinding),

20 physical concentration procedures (magnetic, gravity, and electrostatic separation), physicochemical concentration procedures (flotation), and solid-liquid separation procedures (thickening, filtration and drying).

Hydrometallurgy is carried out in three differentiated and sequential physicochemical stages: (a) selective dissolution of metals contained in the solid phase (leachate); (b) purification and / or concentration of the solutions

Aqueous comprising the target metals (precipitation, cementation, ion exchange, or solvent extraction); and (c) selective recovery of metals (electrodeposition, electrorefining, and hydrogen reduction).

The application of hydrometallurgical routes in the recovery of metals has increased significantly in the last fifty years, and this increase is strongly linked to the fact that high quality deposits are already being explored, and as a result, the qualities are becoming worse and minerals even more

30 complexes, which needs preconcentration stages. In addition, this alternative has a lower environmental impact and is less intensive in capital cost requirements when compared to traditional pyrometallurgical procedures.

The extraction of a soluble fraction of an insoluble solid component by a solvent is generally referred to as leaching, and it is a matter transfer process. Taggart apud Arbiter, in Copper Hydrometallurgy

35 Evolution and milestones, Hydrometallurgy-Fundamentals, Technology and Innovation, 1993, pp. 549-565, define it as the operation in which there is an effective contact between the ore to be leached and the solvent.

Leaching can be carried out under ambient conditions, or at elevated temperatures and / or under pressure. The conditions of the procedure depend on the chemical reactions that occur. In all cases, the objective is to produce ions or metal complexes that can be selectively extracted from the solution.

40 In a leaching process, any reagent used as a solvent must meet at least the following qualities, as described by Gupta et al. in Hydrometallurgy in Extraction Processes, vol I, p. 39,

• You must dissolve the minerals fast enough so that the procedure is economically feasible, and preferably it must be chemically inert to the minerals in the bargain.

• It must be cheap and easily available in large quantities. 45 • If possible, it should be regenerated in post-leaching stage procedures.

In addition to water, which is used to leach soluble chlorides or sulfates, very different solvents have been used in different leaching applications, as shown in the examples in Table 1 below.

Classification of leaching agents

TABLE 1

Category

Reagent Application

H2SO4 diluted

Copper oxides, zinc oxide, lateritic nickel

H2SO4 diluted with oxidant

Sulfides of Cu, Ni and Zn, oxidized uranium ore

Acids

Concentrated H2SO4 Concentrated sulphide copper, laterites,

Nitric acid

Cu, Ni and Mo sulphides, uranium concentrates, zirconium oxide

Hydrofluoric acid

Columbite-Tantalum Ore

Hydrochloric acid,

Titanium ores, nickel matte, reduced cassiterite

Alkalis

Sodium hydroxide, Bauxite

Sodium carbonate

Uranium oxide, Scheelite

Ammonium hydroxide

Nickel sulphide, copper sulfide, reduced laterite

Sulfate / Ferric Chloride

Base metal sulphide concentrates

You go out

Copper chloride Base metal sulphide concentrates

Sodium or potassium cyanide

Gold and silver ores

Ferrous chloride

Nickel sulphide

Water

Water

Sulfides and chlorides, sodium vanadate, sodium molybdate, sodium tungstanate

Acids such as sulfuric, hydrochloric, and nitric acid are the most commonly used acids in dissolution processes such as leaching. Of these, sulfuric acid is the most commonly used and the least expensive.

As the person skilled in the art knows, according to Perry and Chilton in the Chemical Engineer's Handbook, leaching systems can be classified according to the leaching cycle (discontinuous, continuous, or intermittent multilote); according to the direction of the flow (in parallel, countercurrent, or hybrid current); by the type of stages (a single stage, multistage, or differential stage); and by the contact procedure (percolation or dispersed solids).

10 In a multi-stage, countercurrent system (Foust et al., Principles of Unit Operations, 1960, pp. 4349), the two phases enter through the opposite ends of a series of equilibrium stages, as shown in SCHEME 1 next. The phases flow in opposite directions to each other. In this way, the concentration of solute in the product phase L can be increased, and a greater recovery of solute with a smaller amount of solvent is possible.

With respect to the contact method, the leaching can be grouped into in-situ leaching, leaching in a pile or leaching in a debris, (percolation leaching) and leaching with agitation (at atmospheric pressure and under pressure).

IN FLOW DIAGRAM 1 below, it is generally possible to verify how many unit operations can be associated with the main leaching procedures currently available for the treatment of ores and 20 concentrates according to Esteban Domic in Hydrometallurgy - Foundations, processes and applications, 2001.

The leaching in situ consists in applying a leaching solution directly in the place where the ore is located inside the tank itself, without the need to extract it.

Heap leaching is possibly one of the oldest procedures, the oldest being used in the

5 copper recovery. In Spain it has been used since the 16th century for copper recovery. In this leaching procedure, the ore, which has normally been agglomerated before with concentrated sulfuric acid, is stacked, and the leaching solution is applied to the top of the pile, through which it percolates by gravity, collecting at the foot of the battery. The application and distribution of the leaching solution is carried out on the top of the stack by means of drippers or oscillating sprinklers. The irrigation system is defined as a function of evaporation and

10 water availability. The solution containing the target metal is sent to subsequent purification / extraction steps. Heap leaching is used for crushed ores, while heap leaching is used for ROM (run on mine). Debris leaching, which is very similar to the procedures described above, consists of treating ores with very low qualities of the target metal, usually below the economical cut quality for the processing line

15 main, known as mineralized residue. In the heap leaching procedure, the batteries can be both dynamic and permanent. In the case of dynamic batteries, also called on-off batteries, in which the already leached ore is removed to a location for the final discharge of the sludge, the battery base is reused. In the case of permanent batteries, or static batteries, the new battery is formed over the previous ones, using or not the existing waterproofed area.

20 The leaching in bat (in static tanks) comprises a set of tanks of square cross-section into which the leached material is introduced, and the leaching solution is applied so that it flows with upward or downward flow, thus flooding the ore layer It is a very dynamic system suitable for leaching minerals that have rapid dissolution kinetics. Normally, the leaching cycle lasts 6 to 12 days.

25 Leaching with stirring, both at atmospheric pressure and under pressure, requires that the ore be finely

crushed, and is carried out in tanks where solids are dispersed in the leaching solution by gas injection or mechanical agitation. Compared to the rest of the procedures, the leaching time is shorter due to the small particle size (greater specific surface area) and the turbulence of the tank, which provides sufficient diffusion between the reagent and the ore.

Two important differences are evident between the leaching in the pan and the leaching with agitation. In the first place, in leaching with agitation, the liquid is the continuous phase and, secondly, this form of leaching takes place in turbulent conditions, while in the leaching in bat the flow is usually of the laminar type. There is, therefore, an important difference between the rates of matter transfer in both types of leaching. The largest transfers of matter are achieved in turbulent contact conditions.

The application of heap leaching as a procedure for the extraction of gold (cyanidation in alkaline medium), copper, uranium, nickel (leaching with sulfuric acid in acid medium), and other minerals has increased in recent years, due to the possibility of treatment of very low quality minerals that would not be economically feasible by conventional procedures, and also because it is an alternative to the treatment of minerals that have very slow dissolution kinetics.

Heap leaching for copper is widely known. Historically, the pioneer method was used in the mines of Rio Tinto, in Spain, approximately 300 years ago.

In copper-leached leaching, the ore is crushed, then agglomerated with concentrated sulfuric acid, and stacked on a base that has been properly prepared and waterproofed. The heights of the stack vary greatly, between 1.5 m and 30 m. The leachate solution (diluted sulfuric acid) is sprayed on the top of the stack, and percolates by gravity descending through the ore. The charged solution containing the solubilized copper is collected and sent to a copper collection circuit which, typically, is a solvent extraction and electrodeposition circuit. This is a well known procedure, and the set of unit operations of heap leaching / solvent extraction / electrodeposition has been applied on a commercial scale for more than 40 years.

Regardless of the type of ore, the processing path in which the solubilization stage of the target metal is carried out by heap leaching requires the crushing / grinding steps. For processing, it is very important that the battery has good permeability, with good contact between the ore and the solution. As well recorded in US5077021, minerals that contain large amounts of clay or fine-grained minerals (usually material below 0.15 mm) have problems in these types of procedures, because they tend to slow down and even stop percolation in certain areas of the battery, as a result of the blockage. It is common knowledge that the blockage is due to the segregation of materials, where fine-grained materials and / or clays migrate to certain areas inside the stack, thus creating areas with markedly different percolation rates. As a consequence of this effect, the solution begins to follow flow paths of less resistance, creating preferred flow channels. The creation of these preferred flow channels leaves the battery areas unchanged, with a consequent lower recovery of the target metal. The formation of a "suspension" due to the fine particles released and / or clay minerals, when very important, tends to block. Therefore, it is mandatory that the bed becomes permeable during the procedure, either by removing the fine-grained materials and / or the clays or by agglomerating them. The post-crushing agglomeration stage, such as the preparation of the ore for stacking, is a fundamental and inherent point in the heap leaching route for any ore, be it gold, uranium, vanadium, silver, copper, zinc , or nickel, oxide or sulfide ores.

As all those skilled in the art know, nickel ores can be classified into two main types depending on their composition, namely sulfur and laterite (the latter is also known as oxidized). Originating in the underground layers below the saprolitic region (a region rich in clays), sulfur deposits correspond to approximately 20% of Western nickel reserves, and are mainly found in Australia, followed by Canada, China , South Africa, and Zimbabwe. Approximately 55% of total nickel production comes from sulfide ores.

Laterite is produced in more superficial regions. The deposits are found mainly in Brazil, Cuba, Australia, New Caledonia, and the Philippines, with average qualities of approximately 1.95% and an iron oxide content greater than 24%, and presence of cobalt and magnesium. Laterite ore corresponds to approximately 80% of known nickel reserves.

The growing concern about ore production and the reduction in extraction costs has led to increased use of nickel ore from lateritic sources. Two factors contribute to the increasing use of these ores: nickel sulphide reserves imply higher extraction costs, and laterite ores have higher qualities of nickel than sulphide ores, allowing greater efficiency, as shown in the Table 2 following:

50 TABLE 2

Mena (1,000 T)

Quality (%) Nickel (1,000 T) %

Sulfide

10,594 0.58 62 31

Laterite

10,382 1.34 140 69

Total

20,976 0.96 202 100

Source: Mineraçâo e Metalurgia, May 2000.

Laterite ores can be treated both hydrometallurgically and pyrometallurgically. Normally, these procedures involve high energy consumption, as in the case of smelting, the smelting for the production of Fe-Ni, and the processes of leaching with ammonium, which make laterite ore processing non-economical With low nickel content. High pressure sulfuric leaching implies lower energy consumption, but requires a high investment in both equipment and that due to the highly corrosive environment.

Currently, leaching with ammonia and leaching with sulfuric acid under pressure are the two main hydrometallurgical techniques used for the recovery of nickel and cobalt from laterites. In addition to the relatively aggressive chemical treatment and the high capital investment involved, they are strongly dependent on the costs of fuel and sulfuric acid / sulfur, respectively.

Although the pressure leaching process with sulfuric acid does not represent a significant gain in terms of capital costs, compared to more conventional techniques, it allows obtaining a significant economic advantage in terms of operating costs. The procedure also allows a recovery of larger amounts of cobalt, generating enough energy for the operating cycle, but requires much larger production scales,

High nickel and cobalt prices have also prompted the industry to seek alternative procedures to reduce operating costs, so that business profitability is maintained at lower price levels for nickel and cobalt.

The great interest aroused by nickel production in recent years has led to the development of a wide range of new processing routes for the treatment of lateritic ores, such as heap leaching, among others. Heap leaching is an operation that involves low operating costs and investments, is well known, and is widely applied to the ores of copper, uranium and gold.

Although widely used, conventional techniques for the extraction of metals from lateritic ores can make the process economically unfeasible, mainly due to the variability in the prices of fuels and acids needed in such procedures

The use of heap leaching for lateritic ores represents a technological milestone for the nickel industry, because not only does mining of small or low-content deposits become economically feasible, but it is also an alternative mineral processing that requires an investment. sufficiently minor when compared to the conventional procedures mentioned above.

Although they have already been studied and published in other documents, such as in patent procedures GR 1001555, GR 1003569T, US 6312500, WO96 / 031422 and WO 2005/005671, the concepts of heap leaching as proposed in these documents present Processing conditions and system configurations completely different from those proposed in this patent application, as will be evident in the descriptive report.

The first studies related to this application were carried out by S. Agatzini and have their origin in the Greek patent GR 100155. The document describes two heap leaching techniques applied to ores that contain low concentrations of nickel. Technique I takes into account a circuit option whereby the leaching solution is recirculated, that is, it is applied to the ore in a number of contacts until no increase in the nickel concentration is observed in the processing effluent. After this stabilization, a new solution is prepared that is applied to the ore. The solvent used is sulfuric acid, and the initial concentration of the acid solution is 1 N. Percolation rates of about 4 to 33 l / h / m2 are considered, preferably between 12.5 and 25 l / h / m2. As described in this technique, in general, the solution resulting from the leaching process is diluted, with low concentrations of metals, and this is strongly dependent on the type of ore and the processing steps. Technique II basically solves the same procedure described in technique I, and includes a correction of the pH of the leaching solution after each recirculation, before being reapplied to the stack. The pH is corrected to its initial value. The leaching process is considered completed when there is no further increase in the nickel concentration of the solution. The resulting solution can be used later to

leach another material in exactly the same way, until the desired nickel concentration in the solution is achieved. It is emphasized that the technique presented with continuous recirculation does not inhibit leaching, except when the solution is saturated with a specific element, in which case precipitation is observed in the form of a chemical sediment. According to this technique, during the heap leaching process of laterite nickel ore, aluminum is the first metal to precipitate after saturating the solution.

GR 1003569T describes almost the same characteristics described in document GR 1001555, where tap water is replaced by water with different chemical compositions, or municipal / industrial effluent water, or even seawater, which supposedly does not affect the extraction of nickel and also increases the amounts that can be recovered from Mg, Ca and Na of the percolated liquor.

US 6312500 presents a heap leaching process for lateritic nickel ores containing a substantial amount of clay materials, which is defined substantially as a maximum of 25% clays. If necessary, the ore is crushed to the desired size, less than 25.0 mm, preferably between 19.0 mm and 3.35 mm. The process includes an agglomeration stage prior to the formation of the cell, with sulfuric acid, due to the fine material present in the ore. The agglomeration is carried out with conventional equipment, or in any unit that allows the use of this unit operation. Alternatively, after agglomerating, the ore is cured. Curing time may vary between one hour and three days. This stage is carried out by depositing the agglomerated ore in an open area, outdoors. The agglomerated ore is then stacked to form a pile whose height can be between 60 cm and approximately 9 m. Two or more batteries can be formed. The acid solution is applied to the top of the battery, at a speed of 10 to 20 l / h / m2. The leaching procedure itself is described as follows: The first stack is leached with a recent solution of H2SO4 having a concentration of at least 10 g / l. If the pH of the leach effluent solution in the cell is greater than 2 (or the free acid is less than 1 g / l), then the solution can be redirected to the recovery of nickel. If the pH is less than 2, the liquor is directed to the battery 2. In addition to the liquor from the battery 1, a new solution of H2SO4 (with a concentration of at least 10 g / l) is applied to the battery 2. The liquor from battery 2 is also analyzed to determine free acidity. If the pH is greater than 2 or the free acid is less than 1 g / l, then the liquor can be redirected to the recovery of nickel. With these levels of acidity, it is not necessary to subject the liquor to a subsequent neutralization step, since nickel can be extracted directly from the solution, for example by ion exchange. Most of the liquor is subjected directly to nickel extraction, but a portion is still directed to a third battery. The procedure can continue for several batteries.

Although in WO 2004/031422 it is stated that the process is not specific to nickel, this element is included in one of its claims. It is claimed that the ore must be agglomerated. The claimed leachate solution contains sulfuric acid and dissolved sulfur dioxide, and the solution is purged to the nickel recovery circuit, where said sulfuric acid from the leachate solution has a concentration of approximately 785 g / l. In the present invention, sulfur dioxide is added to the leaching solution before application to the cell.

WO2006 / 119559 describes a method of extracting nickel and cobalt from ores of nickel-ferrous oxide by means of heap leaching comprising the steps of shaping the ores of nickel-ferrous oxide into one or more piles, leaching the ore pile with a solution of leachate where the leachate solution includes an acid-enriched hypersaline water as a leach, the hypersaline water having a total concentration of dissolved solids greater than 30 g / l, and recovering the nickel and cobalt from the resulting heap leach. However, this document does not describe that the heap leaching system is operated continuously and that it comprises two or more stages.

The publication "A new method for recovering valuable metals from low grade nickeliferous oxide ores" Hydrometallurgy, (2005) Vol 80, No. 4 pp280-285 by Xu et al. It refers to a process for extracting nickel from low-quality nickel-ferrous oxide ores comprising the steps of hydrolysis with sulfuric acid and leaching with water in a three-stage countercurrent percolation process. However, this document does not describe heap leaching as such.

Objectives and advantages of the invention

The patent application at the time of its granting, unlike the others mentioned above, proposes a continuous processing procedure, in which the ore leaching is carried out in a countercurrent system comprising a minimum of 2 stages, each stage being represented either by a stack section or by a stack.

The objective of the present invention has been to develop a very competitive option to extract nickel, cobalt, zinc, and copper, among other basic metals, from laterite ores, with a lower investment and lower operating costs than those of other technological routes established, as well as solve, economically, the problem of extracting nickel from a low quality ore and / or small deposits.

Another object of the present invention has been to significantly reduce the consumption of sulfuric acid in the system, reaching levels of 350 kg of acid per tonne of treated ore, with variable nickel extractions of 70% at

90% depending on the mineralogical composition, in addition to providing a shorter leaching cycle and favoring the hydraulic balance of the system, and presenting an improved selectivity for the extraction of the target metals with respect to the bargain, and drastically reducing the total volume of solution.

The invention comprises a continuous process in which the leaching of the ore is carried out in a countercurrent system comprising the use of a minimum of 2 stages, each stage being represented either by a stack section or by a stack, which is It can be applied to ores that contain large amounts of natural fine material, and that is an option for the treatment of thick fractions (> 0.5 mm) as well. Such a leachate is presented as an optimal alternative for the extraction of nickel, cobalt, and zinc, among other basic metals, from a laterite ore, with a lower investment and lower operating costs than those of other routes established technology, as well as to solve, economically, the problem of extracting nickel from a low quality ore and / or small deposits.

Description Summary

The invention comprises a process for extracting nickel, cobalt, and other metals from laterite ores by heap leaching, characterized in that it is composed of crushing (I), which obtains a maximum grain size between approximately 25.0 mm and approximately 50.0 mm in secondary crushing, and a maximum grain size between approximately 12.5 mm and approximately 6.30 mm in stages of tertiary crushing, agglomeration (II), stacking (III), and heap leaching ( IV), this last stage being a continuous countercurrent system, and dynamic leaching in a stack with one or more stages presenting two phases, one of which is composed of the ore (solute) and the other composed of the leaching solution, or solvent, which are supplied at opposite ends of the series of stages and flow in opposite directions until the leaching is finished in the last stage, its solute is removed and a new stage is introduced in the first to position, formed by the new ore (solute) to be leached by the solvent solution, which is introduced from the last stage, percolating or flowing through all the previous stages until it reaches the first stage, separating when loaded with metals target (PLS - mother leaching solution).

Detailed description of the invention

The invention comprises a process for the extraction of nickel, cobalt, and other metals from lateritic ores by heap leaching, which comprises a continuous process in which the leaching of the ore is carried out in a countercurrent system comprising the use of a minimum of 2 stages, each stage being represented either by a stack section or by a stack, which can be applied to ores that contain large amounts of natural fine material, and is an option for the treatment of coarse fractions (> 0.5 mm) too. Such a leachate of this type presents itself as an optimal alternative for the extraction of nickel, cobalt, and zinc, among other basic metals, from a laterite ore, with lower investment and lower operating costs than of other established technological pathways, as well as to solve, economically, the problem of extracting nickel from a low quality ore and / or small deposits.

DIAGRAM 2, annexed to this document, is a block diagram that schematically represents the overall flow chart of the process for obtaining a solution rich in the target metal; and DIAGRAM 3, annexed to this document, is a schematic drawing of the authentic countercurrent heap leaching stage.

The present invention comprises a hydrometallurgical processing path for the treatment of nickel lateritic ores, in which the solubilization step of the valuable metals is carried out by heap leaching.

DIAGRAM 2, annexed to this document, is a schematic representation of the overall flow chart of the process for obtaining a solution rich in the target metal. In general, the complete pathway comprises the stages of crushing (I), agglomeration (II), stacking (III), and heap leaching (IV).

The ore as it leaves the mine, ROM [run of mine] (O), is crushed to have a grain size suitable for the procedure. Crushing is carried out with the steps that are necessary to achieve the appropriate grain size for the procedure, depending on the characteristics of the ore. A maximum grain size between approximately 25.0 mm and approximately 50.0 mm is obtained in a secondary crushing, and a maximum grain size between approximately 12.5 mm and approximately 6.30 mm in a tertiary crushing. In the case of more compact and more competent ores, quaternary crushing can be used to provide a larger reaction surface. In these unit operations the generation of fines should be minimized.

FIGURE 1, attached to this document, illustrates a type of high porosity ore, which facilitates the accessibility of the leaching agent.

Then, the crushed product is sent to the agglomeration unit (II) by means of a conveyor belt. If necessary, water can be added to the ore during transport, for example in cases where the ore is very dry and contains a high amount of fine material. The addition of water to the conveyor belt can be carried out in different ways, such as spraying, and minimizes the formation of dust, thus making working conditions more favorable. Additionally, and this is very important, it minimizes the loss

of nickel, since the concentration of this element in the finer fractions is a characteristic of lateritic ores. The agglomeration is carried out with conventional equipment, such as drums or rotating discs, or even equipment that provides the expected result.

At this stage, sulfuric acid, both concentrated and in solution, and water are added to the ore in amounts that are defined according to the amount of fine material present (which can be 30-70% less than 0.074 mm), where The acid and water are added in dosages that are sufficient to produce the desired amount of agglomeration moisture. The humidity of agglomeration has been determined previously, in laboratory tests, and depends on the physical and mineralogical characteristics of the ore. Due to the ultrafine fraction present, a binding agent can be added, which can be organic or inorganic, natural or synthetic, or even of mineral origin, such as bentonite, for example, provided that said agent is inert to the acid in the leaching solution. . In the agglomerated product there should be no fine material, which means any fraction of the ore less than 1.70 mm.

It is worth noting that ores that have natural basicity due to the high proportion of basic constituents, such as MgO or CaO, have a high neutralizing capacity, and this is the case of saprolitic ores. Therefore, in addition to the already well-known advantages of agglomeration, this stage is also important in the proposed route, as a stage of prior neutralization of the ore. The amount of sulfuric acid to be added is defined taking into account the main acid-consuming species in the granulometry of the process. This neutralizing action at this stage accelerates the beginning of the extraction of the target metals. When acid addition is not performed at this stage and agglomeration is carried out exclusively with water, with the presence or absence of binding agents, a delay in the extraction of the target metals, especially nickel and cobalt, is observed, although it is not observes a significant impact on the total leaching cycle. Normally, magnesium, iron, aluminum, and calcium are the main acid-consuming species.

After agglomerating (II), the ore is stacked (III), forming piles whose final height is between 2 m and 7 m, preferably 4 meters.

The proposed leaching system (IV) is carried out in dynamic (or on-off), countercurrent, multistage batteries, where the number of stages is 2 or more, preferably 3 stages. The system described in this document follows the conceptualization presented by Foust et al in Principles of Unit Operations, already mentioned in the description of the state of the art. As it is a unit leaching operation, the two phases comprise the ore (solute) whose content in valuable metals (specifically Ni and Co) is to be extracted, and the sulfuric acid solution (solvent). The two phases feed on opposite ends of a series of equilibrium stages, and flow in opposite directions to each other. With this technique, higher concentrations of Ni and Co are obtained in the product of the liquid phase, as well as a shorter leaching cycle, and a smaller amount of solvent is used, compared to the circuit flows in simultaneous current or parallel flow.

The new leachate solution - a solution of sulfuric acid that varies from approximately 50 g / approximately 200 g / l - is applied to the top or outer surface of the last stage battery, or stage 3 in the case of a three-stage system, and the percolated solutions of each stage are collected separately, in individual tanks, and used in the next stage according to the flow direction.

The solutions of steps 2 and 3 are designated as intermediate solution 2 (ILS2) and intermediate solution 3 (ILS3) respectively, and so on.

The final solution containing the target metals - the mother leach solution (PLS) - has a residual acidity between approximately 10 and approximately 30 g / l.

At the end of the leaching procedure (IV), in the last stage, or of stage 3 in the case of a 3-stage system, the ore is washed well with new water or process water. After washing, the leached ore is transported to a previously waterproofed area and prepared for final deposition of the leachate residues. It is important to understand that, since it is a continuous procedure, as soon as the leaching of the ore stops at the last stage, or in stage 3 for example, the ore that was in stage 2 goes to stage 3 , and the one in stage 1 goes to stage 2, and a new section (or stack) is introduced in entapa 1.

The heap leaching process, which is the objective of the present invention, can be applied to ores that contain large amounts of natural fine material, and is also an option for the treatment of coarse-grained fractions (e.g., a size of the grain greater than 0.5 mm). In the latter case, the fine grain fraction would undergo conventional treatment in a high pressure autoclave, or atmospheric leaching, or a combination of the two leaching procedures.

The invention also takes into account the final product containing nickel, cobalt, and other metals from laterite ores, obtained by a heap leaching (IV) process, or the solution obtained with the target metals (PLS) obtained in the procedure according to the invention, already notified.

Different alternatives have been evaluated for the treatment of the mother leach solution (PLS), the effluent solution of step 1 - for example, production of mixed precipitate, or verticalization of the process until

metallic nickel production.

The mother leach solution is subjected to extraction of the iron and aluminum present, by stepwise precipitation with the addition of an alkaline reagent. Then, the solution free of iron and aluminum, or at least containing acceptable levels thereof, is sent to the nickel and cobalt extraction stage (6), which can be extracted or recovered by various techniques, such as precipitation, solvent extraction, or even ion exchange. With solvent extraction, or an ion exchange resin, metallic nickel is obtained; With precipitation, a mixed hydroxide or sulphide of nickel, cobalt, zinc, and other basic metals is produced.

The present application refers to certain operating conditions, such as the height of the pile, the size of the grain of the ore, and the concentration of sulfuric acid among others, without limiting its exclusivity, and emphasizing that these conditions may vary in each one of the leachate stages in the stack without negatively affecting the final result of the procedure.

Although a preferred operating procedure has been described and illustrated, it is emphasized that alterations of said procedure are possible, and can be executed, without departing from the scope of the present invention.

Example 1

To evaluate the applicability of leaching in a pile at a rejection fraction (> 0.5 mm) from the benefit of a laterite ore by the HPAL / atmospheric leaching route, three mixtures were composed whose chemical analysis is presented in TABLE 3 below , and which were tested in columns 1 m high.

Chemical analysis of food samples

TABLE 3

Description

At (%) Co(%) Cr (%) Cu (%) Faith (%) Mg (%) Mn (%) Neither (%) Yes (%) Ti (%) Zn (%)

Sample 1

0.83 0.03 0.58 0.02 9.65 1.55 0.21 0.31 33.65 0.05 0.02

Sample 2

0.72 0.03 0.67 0.03 8.54 9.52 0.11 0.46 25.10 0.03 0.03

Sample 3

2.37 0.09 0.78 0.06 10.20 6.42 0.37 1.36 24.70 0.24 0.05

GRAPH 1, annexed to this document, shows the distribution of nickel in these samples. Nickel is found mainly in phyllosilicates (serpentines and chlorites).

It was determined that 100% of the sample size was less than 1.27 mm. Grain size distributions are shown in GRAPH 2 annexed to this document. The rest of the conditions for carrying out these tests were the following: percolation rates of 10 l / h / m2; concentration of sulfuric acid in the leaching solution, 20 g / l; dosage of acid in the agglomeration, 20 kg / ton of ore; Open circuit tests.

These preliminary tests indicate the potential for nickel extraction by means of a unit operation delixiviado in stack. However, the nickel extraction curves in FIGURE 3, attached to this document, show that the system needs more acid, for example, by a solution of leaching at a higher concentration. The low acid concentration may be a factor of slow kinetics. In 100 days of operation, samples 1, 2 and 3 reached 34%, 58% and 69% of nickel extraction, respectively.

Example 2

The tests were carried out in columns 1 m high, and also in columns 4 m high to make a preliminary assessment of the influence of height on nickel extraction. These tests were carried out on samples with four different lithologies, and also on a sample composed from the individual lithotypes. All samples were crushed to obtain a grain size that was 100% less than 12.5 mm. The percolation rate was constant and equal to 10 l / h / m2. The concentration of sulfuric acid in the leaching solution was 20 to 200 g / l in the 1 meter high columns, and 50 g / l in the 4 meter high columns.

Nickel extraction curves for different types of minerals, under different acidity conditions, confirmed the influence of these variables on the procedure. Higher acid values lead to faster kinetics.

Nickel extraction varied according to mineralogy. The mineralogy that was less sensitive to processing, and thus provided the lowest levels of nickel extraction, was the one with a significant amount of nickel in iron hydroxides. This level of sensitivity is understood in terms of the form of presentation of Ni, which in the crystalline structure of iron hydroxide requires more energy in the system to overcome the high binding energy of said hydroxides. Ni atoms are less accessible to the leaching solution.

GRAPH 4 (nickel extraction from a saprolitic ore) and GRAPH 5 (nickel extraction from a ferruginous or limonitic ore), annexed to this document, show the extraction curves for tests 5 performed on columns 1 m high , for two of the types of ore evaluated.

The tests carried out in miniature columns allowed to evaluate the maximum possible extraction of nickel achieved. As all types achieved stabilization in 100 cycle-days, this time was considered the total cycle, and the acid concentration was varied every 20 days, from 20 to 200 g / l and after 200 to 20 g / l. The influence of the acid concentration on the procedure was reconfirmed. In trials conducted with

10 increasing acid values, it was observed that the inflection of the curve had increased. In trials with decreasing acid values, it was observed that the effect was not significant.

In these trials, three main stages have been identified in the evaluation leaching procedure, primary leaching, and secondary leaching, as shown in FIGURE 6 (leaching stages) annexed to this document. In the last stage, the main reactions involve the minerals that solubilize with

15 facility, especially species containing magnesium, and therefore this stage has been identified as a neutralization. There are three different kinetics, depending on how the nickel has been distributed among the minerals: Ni absorbed between the plates (between plates) of phyllosilicates is extracted more easily than the nickel of the structure (intra-plate) of the same minerals, which in turn provide greater extraction than nickel contained in iron hydroxides.

20 This behavior of the different leaching zones indicates the importance of evaluating the circuit according to the countercurrent principle.

GRAPH 7, annexed to this document, shows the nickel extraction curves obtained for the four typologies, for tests on 4 m high columns.

Example 3

25 Three different leaching circuit options were evaluated, whose extraction curves are presented in FIGURE 8 annexed to this document: open circuit, three-stage countercurrent circuit (circuit with ILS) and circuit with PLS recirculation and concentration correction of acid.

In the ILS circuit, a total cycle of 150 days with 3 stages of 50 days each was considered. The countercurrent circuit (ILS) constitutes itself as the best alternative for the evaluated ores, shortening

30 substantially the leaching cycle and decreasing the total volume of solution, as well as acid consumption, as shown in the following TABLE 4:

TABLE 4

Circuit type

Leachate cycle (days) Extraction Ni (%) Co Extraction (%) H2SO4 consumption (kg / tonne of ore)

ILS

150 84 70 280

Open

270 87 72 560

With recirculation and acidity correction

270 84 70 250

Example 4

35 Tests were carried out with the same sample, in columns 4 m high, to assess the influence of grain size on nickel extraction. The rest of the process conditions, such as the concentration of the leaching solution, percolation rate, agglomeration conditions, were kept constant. It was observed that, for very porous samples in addition to the fine materials naturally present in the ore, there is no significant impact on nickel extraction from a size larger than 12.5 mm or 50.0 mm, such

40 as shown in GRAPH 9 (evaluation of the influence of grain size on nickel extraction) annexed to this document.

Claims (17)

one.

Procedure for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching, characterized in that it comprises a crushing (I) that obtains a maximum grain size of between approximately 25.0 mm and approximately 50.0 mm in a secondary crushing, and a maximum grain size between approximately 12.5 mm and approximately 6.30 mm in stages of tertiary crushing, agglomeration (II), stacking (III) and heap leaching (IV), the latter being stage a continuous heap leaching system in countercurrent with two or more stages, which has two phases, one of which is composed of the ore (solute) and the other composed of the leaching solution, or solvent, which are supplied in opposite ends of the series of stages and flow in opposite directions until, at the end of the leaching in the last stage, its solute is removed and a new stage is introduced in the first position comprising ore new (solute) to leach through the solvent solution that is introduced from the last stage, percolating or flowing through all the previous stages until it reaches the first stage, which separates if it is loaded with target metals (PLS).

2.

Procedure for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that the crushing (I) can be carried out with as many steps as necessary to get the right grain size for the procedure.

3.

Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that, optionally, water can be added to the crushed product before being sent to the stage of agglomeration (II).

Four.

 Process for the extraction of nickel, cobalt and other metals from laterite ores by leaching in a pile according to claim 1 characterized in that, during the agglomeration stage (II), there is addition of water and, of optionally, of acid or other additives, such as binding agents, among others.

5.

 Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 4 characterized in that the sulfuric acid, concentrated or in solution, and the water are added in dosages that They are enough to get moisture from agglomeration.

6.

Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 4 characterized in that the binder can be organic or inorganic, natural or synthetic, or even of origin mineral, such as bentonite.

7.

 Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to any of claim 1 or claim 4, characterized by the fact that free fines are not present in the agglomerated product. negatively affect the percolation process.

8.

Process for the extraction of nickel, cobalt and other metals from laterite ores by leaching in a pile according to claim 1 characterized in that the batteries are preferably of the dynamic or "on-off" type.

9.

 Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to any one of claim 1 or claim 8, characterized in that the stacked ore (III) constitutes stacks with heights between approximately 2 m and approximately 7 m.

10.

 Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that the heap leaching system

(IV) comprises three stages.

eleven.

Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that the new leaching solution comprises sulfuric acid solution.

12.

Process for the extraction of nickel, cobalt and other metals from laterite ores by leaching in a pile according to claim 11 characterized in that its concentration is between 50 g / l and 200 g / l.

13.

Procedure for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that the new leaching solution is introduced in the upper face, or in the upper part , of the last stage.

14.

Process for the extraction of nickel, cobalt and other metals from laterite ores by leaching in a pile according to claim 1 characterized in that the percolated solutions of each stage (ILS) are collected separately and used in The next stage, according to the flow direction.

fifteen.

Process for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that the mother leaching solution

(PLS) has a residual acidity of between about 10 g / l and about 30 g / l.

16.

Procedure for the extraction of nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized by the fact that at the end of the leaching process in the last stage, the leach ore is washed well with new water or with process water, and then

5 is considered as waste. 17. Procedure for extracting nickel, cobalt and other metals from laterite ores by heap leaching according to claim 1 characterized in that the solution obtained with metals (PLS) can be subjected to a subsequent process to separate metals such as nickel, cobalt, zinc, aluminum and iron, among others. FIGURE 1 Solution (Solution of